Engine-generator set

ABSTRACT

A generator support plenum and engine-generator set for installation on a pickup truck in an RV or on a boat, for example, sits in or under or forms a part of an enclosure for the engine-generator set and defines cool air flow paths into the set for cooling the engine and generator and aspirating the engine. The plenum also defines a warm air outlet duct for escape of the cooling air. In the outlet duct a diffuser couples to the exhaust of the engine to mix hot exhaust with the much cooler escaping cooling air that has passed over the engine and generator. The diffuser eliminates the effect of the extreme hot exhaust gas and muffles the engine sound. Insulation coating the internal surfaces of the plenum further suppresses engine noise.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority from the provisional patent applicationSer. No. 60/470,011 filed May 12, 2003 in the name of Gerald S. Piercey,III entitled “Compressor Mount Plenum” incorporated herein by reference.

FIELD OF THE INVENTION

This invention relates to an intake and exhaust plenum for a generatorand more particularly to a plenum that supports the generator.

BACKGROUND

Generators used with recreational vehicles (RVs), on boats and thosemounted on trucks for use at a worksite more often than not areintrusively noisy and direct hot exhaust fumes where they should not. Inolder RV parks, for example, insufficient electrical service often isavailable for when the park is well-filled with newer RVs that boast amultiplicity of electrical appliances, air conditioners and the like.Where that is the case, RV owners typically crank up their owngenerators. Generally these are too noisy for use in a crowded RV park,and often gasoline engine exhaust is directed out the side directlytowards the next door neighbor. When the generator is in or on the RVitself, vibrations as well as noise will plague the RV occupant.Moreover, an on-board generator is (or can be) a fire hazard.

Likewise, at a worksite, noise and noxious exhaust fumes can, again,annoy persons in the neighborhood of a truck-mounted generator. And thegenerator may be run for hours on end. Emission of very hot exhaust fromthe internal combustion engine of an engine-generator set is a hazard toneighbors, pets and close-by objects in a tightly populated camp site orRV park.

A further problem that has arisen in connection with engine-generatorsets used to power electrical appliances on houseboats, yachts and thelike has been the collection of carbon monoxide in living and sleepingquarter. In at least one locality where vacationers regularly renthouseboats, sickness and fatalities have occurred.

RV owners who would appreciate relocation of a noisy generator may notwant an engine-generator set sitting on the tow vehicle. A metal toolboxspanning the bed of a pickup truck directly behind the cab is viewed asaesthetically permissible by RV users and other pickup truck owners, buta freestanding, installed generator is not necessarily so-viewed.

There is a need, therefore, for a generator housing and support thatreduces noise, correctly directs and dilutes engine exhaust and has aneat and acceptable appearance.

BRIEF SUMMARY

The invention relates to a plenum that (1) cools hot exhaust exiting anengine-generator set, (2) channels engine cooling air and air forcombustion into the generator enclosure, (3) mounts or supports thegenerator neatly inside a pickup toolbox or other enclosure, and (4)reduces noise. In one embodiment, a generator support truck for example,the plenum fits within a containment box which is the toolbox of apickup and opens through openings formed in a wall of the box. (By“wall” is meant the box's bottom, lid or any of its upright walls.) Inanother embodiment the plenum supports the toolbox itself within whichthe generator is contained and communicates through openings through atoolbox wall. In a third embodiment the plenum and toolbox are combinedinto a single unit. Removal of the generator to the tow vehicle, awayfrom the RV, reduces the risk of fire and eliminates the vibration ofthe RV. Exhaust can be directed away from the RV and any neighbor.

In the case where an engine-generator set must be located in thegenerator compartment of an RV, the containment box and plenum of theinvention can still improve the problems of noise and hot exhaust gasbeing wrongly directed. In several exemplary preferred embodiments, thebox and plenum with air intake ducts opening to atmosphere draw in airto aspirate the engine and cool the engine and generator, while coolingair being exhausted is intermixed with hot exhaust before expulsion fromthe generator-containing box. In one case the box protrudes through thefloor of the RV generator compartment and has openings into the plenumand out of the plenum through sidewalls just below the floor of thecompartment. In another case floor openings in an RV generatorcompartment align with openings into the air intake duct and out of theair outlet duct.

Hot exhaust from the internal combustion engine is mixed with warmedcooling air that, while warm, is nevertheless very much cooler than theexhaust, and the intermixed gasses are dispersed from an outlet ductformed by the plenum. Diffusers of various shapes and designs can beconnected to the tailpipe of the internal combustion engine driving thegenerator. Holes along the length of the diffuser emit the hot exhaustinto the cooler, cooling air that is on its way to atmosphere. Thusintermixed, the gaseous output from the box that houses theengine-generator set is far cooler and safer than hot exhaust.

The above and further objects and advantages of the invention will bebetter understood from the following detailed description of at leastone preferred embodiment of the invention, taken in consideration withthe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a toolbox-style enclosure for agenerator and housing a generator support plenum;

FIG. 2 is a fragmentary perspective view of the enclosure of FIG. 1 withthe generator removed to expose the plenum;

FIG. 3 is a fragmentary perspective view of the enclosure of FIG. 1 andthe plenum and illustrates aligning openings through the enclosure intothe plenum;

FIG. 4 is a perspective view of the plenum of FIG. 3;

FIG. 5 is a top plan view of the plenum of FIG. 3;

FIG. 6 is a front elevation view of a further embodiment of theenclosure of FIG. 1 with parts broken away for clarity;

FIG. 7 is a side cross-sectional view of a further embodiment of anenclosure and plenum according to the invention;

FIG. 8 is a front elevation view of the enclosure and plenum of FIG. 7;

FIG. 9 is a fragmentary cross-sectional view of an exhaust diffuserlocated in a duct within a plenum in accordance with the invention;

FIG. 10 is a top plan view, partly in cross-section, of the diffuser ofFIG. 9;

FIG. 11 is a fragmentary perspective view of a further exhaust diffuserin a duct in the plenum of the invention;

FIG. 12 is a cross-sectional view of the diffuser of FIG. 11;

FIG. 13 is a fragmentary cross-sectional view of a further embodiment ofa diffuser in a duct in a plenum according to the invention;

FIG. 14 is a top plan view, partially in cross-section, of the diffuserof FIG. 13;

FIGS. 15 and 16 are fragmentary perspective views of a toolbox withgenerator support and cooling provisions in accordance with a furtherembodiment of the invention and showing in FIG. 15 the box open and inFIG. 16 the box closed, both installed in a pickup truck;

FIG. 17 is a diagrammatic illustration of a toolbox-style generatorinstallation in accordance with the invention mounted on a house boat;

FIG. 18 is a fragmentary cross-sectional and diagrammatic viewillustrating a toolbox-type enclosure and plenum for a generatorinstalled through the floor of an RV generator compartment;

FIG. 19 is a fragmentary cross-sectional and diagrammatic view of atoolbox and plenum generator installation installed within an RVgenerator compartment and opening through holes in the compartmentfloor;

FIG. 20 is a cross-sectional top view of a plenum illustrating a spiralwound diffuser;

FIG. 21 is a top cross-sectional view of a plenum illustrating agenerally U-shaped diffuser;

FIG. 22 is a cross-sectional side view of a plenum diagrammaticallyillustrating the U-shaped diffuser of FIG. 21;

FIG. 23 is a fragmentary end view of the box of FIGS. 15 and 16;

FIG. 24 is a top plan view of the box of FIGS. 15 and 16 with lid open;

FIG. 25 is a perspective view with parts broken away for clarity of afurther embodiment of the combined generator plenum and enclosure of theinvention; and

FIG. 26 is a fragmentary perspective view of the plenum and enclosure ofFIG. 24 showing the cool air intake opening therein.

DETAILED DESCRIPTION

In FIG. 1 an engine-generator set 10 supported by the plenum 20 in atoolbox 15. The engine-generator set 10 is referred to on occasion hereas the generator 10 or the “generator” as such usage is common. Acentral wall 22 (FIG. 2) conforms a pair of ducts 23 and 24 to the gasintake and output provisions (not shown) of the engine-generator set 10having an outer case 11.

The duct 23 of FIG. 2 is the air intake duct and fits under openings inthe case 11 (FIG. 1) through which the generator 10 draws cooling airinto the generator enclosure and over the internal combustion engine andgenerator. It, the duct 23, also fits under and opens into an ignitionair intake opening in the generator case 11 that provides air forcombustion within the internal combustion engine that drives thegenerator.

The duct 24 is the air outlet duct that allows the escape of the coolingair and also the exhaust of the generator driving engine. Into the duct24 flows the cooling air exiting the generator enclosure and the hotexhaust from the engine's tail pipe. The escaping cooling air isordinarily warm, but far cooler than the hot exhaust from the engine.The term “warm cooling air” used herein means simply cooling air raisedin temperature by its passage over and around the generator and engine.The mixing of air and exhaust to cool the exhaust is safer forindividuals and objects near to the emergent gases, and it also protectssound-proofing applied to interior duct surfaces for noise abatement. Ina preferred embodiment a diffuser assures the thorough mixing of the hotexhaust into the much cooler escaping cooling air. Specific diffusersfor this purpose are discussed below in connection with FIGS. 9-12.

In FIG. 3 openings 26 and 27 of the plenum can be seen. With the plenumin place in the box 15, the opening 26 that draws in air aligns with anopening 29 in the face of the box. The opening 27 of the plenum alignswith an opening 30 for emission of the intermixed cooling air andexhaust. The central wall 22 stands as a partition between the coolintake air in duct 23 (FIG. 5) and the much warmer and mixed air andexhaust in duct 24 (FIG. 5). A suitable resilient seal runs along thetop of the wall 22 to engage the bottom of the generator case 11 betweenthe intake and outlet openings. Not shown in FIG. 5, the seal may be asoft rubber or rubber-like tubular seal 326 like the seal of FIG. 24.Four short angle irons 35 upstanding at the top of the plenum engagecorners of the generator case 11 to hold the generator 10 in place.These are best seen in FIGS. 4 and 5. Any suitable alternative featurecan be used for locating the generator and keeping it in place such as acontinuous rim around the bottom of the generator case 11. Such a rim isshown in FIG. 26 at 408, for example.

In an alternative embodiment of the invention, as shown in FIG. 6, aplenum 37 supports the entire toolbox 15. The interior ducts and theopenings 26 and 27 are similar to those described above. Openings 38 and39 are cut into the bottom wall of the box 15. These conform generallyin size and shape to the openings 19 and 21 of the plenum as shown inFIG. 2. In this embodiment as well as in that previously described,within the ducts 23 and 24 suitable soundproofing 25 covers everyinterior surface. The soundproofing 25 may be a commercially availableduct insulation and may afford a degree of heat insulation as well,keeping the box outer surface relatively cool.

In yet another alternative embodiment as shown in FIGS. 7 and 8, thetoolbox and plenum are constructed together as a single unit. Thetoolbox 45 is shown with a lid 46. The toolbox bottom 48 serves as thebottom wall of the plenum ducts 50 and 51. The location of theengine-generator set and enclosure is indicated in broken lines at 53. Arear wall 54 for the box 45 serves also as the back wall of the plenumat 56. A wall 57 partitions the cool intake air at 50 from the hot gasesescaping at 51. In FIG. 7, at 58 can be seen the opening by which airpasses from the upper surface of the plenum. Two or more uprightgenerator locating brackets 61 serve to locate the generator and keep itin place. A seal 60 runs along the top of the wall 57 sealing andengaging the bottom of the generator enclosure. As in the boxes of FIGS.1-5, a pair of openings, here 63 and 64, through the face of the boxfront wall 65 open into the ducts 50 and 51, respectively. Soundproofingis visible at 66. The bend in the wall 57 evident in the wall 22 of FIG.2 is seen at 68 in FIG. 7.

It is also envisioned that if the air intake openings, the cooling airoutlet opening and the tail pipe of the generator open through a lid,front, back, side wall or bottom of the generator enclosure, a similarplenum will stand upright next to that wall or have a portion thereofstanding upright next to the wall and be conformed to supply air intothe openings and receive air and exhaust from within the generatorenclosure. Again soundproofing is applied to interior duct surfaces. Theplenum toolbox combination may simply be positioned in the basement ofan RV or in an RV generator compartment to discharge the mixed, quieteddischarge in the downward direction for the RV user who cannot put thebox in his truck but still wants a quiet, sound-proofed installation.The plenum intake and discharge may be in the downward or underside ofthe generator enclosure as described below.

FIGS. 18 and 19 illustrate two alternate arrangements for use of the boxand plenum combination of the invention in an RV generator compartment.In FIG. 18 a box 135 includes a lower plenum 137 that supports theengine-generator set as previously described. A number of mountingflanges 139 secured to sidewalls 140 of the box 135 secure the box 135in an opening 142 in the floor 144 of the RV generator compartment 150.

The lowermost portion of the box 135 that contains the plenum 137protrudes below the floor 144 of the generator compartment. Cooling airintake opening 148 leads into cooling air intake duct 149. The duct 149communicates with the engine-generator set through a pair of openings152 and 154, providing combustion and cooling air as previouslydescribed. Cooling air exits the environment of the engine-generator setthrough an opening 156 and an exhaust diffuser 158 as previouslydescribed. This diffuser 158 disperses exhaust into the lowertemperature cooling air within the air outlet duct 160 for emissionthrough a further opening 162.

In an alternative embodiment seen in FIG. 19, the box 135′ containingthe engine-generator set is contained entirely within the RV generatorcompartment 150. One or more openings 166 formed in the floor 144 of thecompartment 150 provide air intake to the intake duct 149. That air actsas described in connection with FIG. 18 to aspirate the engine and coolthe generator and engine. Cooling air escapes through the opening 156into the duct 160 formed in the plenum and out an opening 168 formed inthe floor 144 of the generator compartment. Suitable securing means 170may be provided to retain the box 135′ in place within the compartment150.

Gasoline and battery power can be taken from the truck or tow vehicle orcan be separately installed in the box 15 of FIG. 1. With a separatefuel tank and battery installed in this box, a completely independentpower source is provided that can be used at a cabin or, e.g., mountainretreat, but that goes home with the owner, for theft prevention, andfor further uses away from the cabin or retreat. In FIG. 6 the box 15 isequipped with the generator's off/on switch 31 and/or ignition keyswitch 32 and/or a RF remote 33 and remotely activated ignition switch34. Also mounted are such meters 36-38 as may be desired. Thesetypically would include engine hours of use, temperature, oil pressure,amperage, without limitation. The RF remote 33 and RF activated switch34 are particularly desirable features allowing activation of thegenerator 10 from within an associated RV, for example.

FIGS. 9 and 10 illustrate an embodiment of a diffuser providing for goodmixing of hot exhaust gas with the cooler, but warm, cooling air exitingthe generator through the duct 24. The diffuser 260 includes an exhaustpipe 261 having linearly arranged openings 263 on opposite sides of thepipe along a length of a pipe extending within the duct 24. A solid orvented end plate 265 is welded across the end of the pipe 261. A pair ofheat shields 267 and 268 protect the plenum walls and its soundproofingfrom the heat of the pipe 261 and the escaping exhaust. The diffuser 260affords good mixing of the exiting cooling air (indicated at 269) withthe hot exhaust from openings 263 of the pipe 261, indicated by theunnumbered arrows in FIG. 10. A set of welds 270 affix a top heat shield267 to the pipe 261 and a set of welds 271 affix a lower, larger heatshield 268 to that pipe.

The diffuser 260 of FIGS. 9 and 10 is preferable for a relativelyshallow duct 24 as depicted in FIG. 9. Where greater depth in the duct24 is available, as depicted in FIG. 11, a diffuser 280 as illustratedin FIGS. 11 and 12 can be used. Like the diffuser of FIGS. 9 and 10, thediffuser 280 has an exhaust pipe 281. A series of holes 283 open fromwithin the pipe 281. Unlike the diffuser of FIGS. 9 and 10, the holes283 are not arranged in just a single linear array, but open, in thisexemplary embodiment, in several directions on each side of the pipe 281as best seen in FIG. 12. The pipe 281 has a closed end 285. At theclosed end 285, a circular plate 286 extends radially outward from thepipe 281. Connected with the plate 286 is a cylindrical shell 288encircling the location of the pipe 281 that has the holes 283. Theplate 286 may close the end of the pipe 281 and the end of the shell288. The plate may have openings venting the pipe and shell ends. Thecylindrical shell 288 has a series of openings 289 larger than theopenings 283 in the pipe 281. These open out of the shell radially in,for example, four directions on each side of the shell as best seen inFIG. 12. Although shown as circular in cross-section, the diffuser ofFIG. 11 can be oval, square, rectangular, etc., in its cross-section.The outer shell 288 provides heat shielding and gives additional mixingof air and exhaust.

Air that is cooler than the hot exhaust and that is being moved by anengine cooling blower or fan in the generator enclosure is driven intothe outer shell 288. It mixes with hot exhaust and the intermixed airand exhaust exits the shell through the openings 289 at a moderatedtemperature. Good mixing of the cooler engine cooling air and hotexhaust results, protecting the walls of the duct 24 and itssoundproofing.

An alternative diffuser embodiment and gas flow arrangement appear inFIGS. 13 and 14. The diffuser 290 includes an exhaust pipe 292 ontowhich a head 293 is affixed. Multiple openings 295 in the head emit hotexhaust against the flow of cooler engine cooling air entering theplenum at 296. The mixed gasses escape downward through an opening 298.

Further exemplary diffuser embodiments are shown in FIGS. 20, 21 and 22.In FIG. 20 a rolled exhaust dispersion tube 175 is shown. An exhaustconnection is diagrammatically indicated at 177 and a series of inwarddirected holes 179 emit hot exhaust in the directions indicated by theunnumbered arrows. The diffuser 175 of FIG. 20 is seen from abovelooking down into the air outlet duct 24.

In FIG. 21 a further, generally U-shaped diffuser 185 is seen, againlooking downward into the air outlet duct 24. An exhaust connection tothe diffuser is diagrammatically indicated at 187. Holes 189 along thelength of the diffuser direct hot exhaust in the directions indicated bythe unnumbered arrows.

A side view of the diffuser 185 of FIG. 21 is illustrated in FIG. 22.There the tailpipe 190 of the generator-driving internal combustionengine (not shown) is seen extending through an upper surface of theplenum where a coupling 192, that may be welded in place, connects thetailpipe 190 to the diffuser 185. In the case of the diffuser 185 shownin FIG. 22, the diffuser is formed from cut and welded sections. Variousshapes and configurations, suited to particular installations, can beobtained.

Use of a diffuser such as the diffusers 260, 280, 290, 175 and 185results in well-mixed gases escaping the duct 24 without hot spots. Inaddition, each of the diffusers 60, 80, 90, 175 and 185 converts thetypical “putt, putt” exhaust sound to a steady hum.

FIGS. 15 and 16 illustrate a further embodiment of the combinationgenerator and toolbox. In FIG. 15 the generator 10 can be seen residingin its own compartment in the toolbox 115. A gas output duct 117 directsthe mixture of exhaust and cooling air directly upward. An opening 119in the lid 118 of the box 115 aligns with the duct 117. In a separatecompartment 121 a dedicated gas tank 122 is shown in broken lines.Alternatively a smaller tank than that shown may be provided leavingroom for a tool area or other storage. Access to the interior of thegenerator may be had through a removable front panel 124 and alignedservice door 125 into the case 11. Access to the generator is availableas well as through the open lid 118 and removable upper cover of thegenerator case 11. In one preferred alternative embodiment of thisarrangement, the removable panel 124 is affixed to the lid and swings upand away from the generator when the lid is opened. Air intake openingsmay be through the wall of the box that faces the cab of the truck. Inthis embodiment, the location of the intake duct openings adds to thequieting provided and the exhaust gasses are expelled upwardly at a highrate of speed, reducing exhaust smells at ground level. FIG. 16 showsthe closed tool box in the back of a pickup truck. The box 118 very muchresembles the typical textured sheet metal tool box generally viewed asacceptable in appearance.

Shown in FIG. 23, the embodiment illustrated in FIGS. 15 and 16 has anair intake opening 301 formed in the right hand side panel 303 of thebox 115 as illustrated in FIG. 23. Optional screening 305 is shown tokeep animals out of the ducts. The box 115 of the particular embodimentis notched on each side as shown at 307 to accommodate the wheel wellsof a short bed pickup truck.

In FIG. 24 the floor of the tank containment compartment 121 has beenremoved and the cold air duct 320 can be seen extending below thecompartment to an opening 322 that provides engine and generator coolingair to the generator 10 and combustion air to the generator driveengine. The partitioning wall 324 is shown having a pair of parallelseals 326 extending along its upper edge. To the left of the wall 324 inFIG. 24 is shown the hot air opening 328 that receives warm cooling airfrom the generator 10 into the duct 330 that extends below the generator10 to an upright duct portion 332.

In FIG. 24 the optional screening shown covering the duct 330 in FIG. 24is broken away and a diffuser 334 is seen having an intake pipe 336 forcommunication with the tail pipe of the internal combustion engine thatdrives the generator. Small holes 338 are formed in a series along thediffuser 334, which in this case is an L-shaped hollow, rectangular incross section diffuser capped at its end 340. From the duct 330intermixed warm cooling air and hot exhaust moves to the upright ductportion 332 and escapes via the opening 119 of FIG. 16.

The embodiment of FIGS. 15 and 16 are particularly suited for such usesas houseboats, large cabin cruisers and the like where noxious fumesraise the possibility of asphyxiation, particularly when occupants sleepand the generator runs. As shown in FIG. 17, an installation of agenerator-tool box combination of the kind illustrated in FIG. 15 on theuppermost deck 128 well above living and sleeping quarters 129. Theupward emission of the exhaust-cooling air mix further moves the carbonmonoxide of the exhaust away from the boat inhabitants and where it ismost likely to be swept away by the breeze.

In one further embodiment illustrated in FIGS. 25 and 26, cold air isdrawn into an enclosure 401 shown in FIG. 25 with its front coverremoved. Cold air is drawn into the enclosure through an opening 403seen in FIG. 25. A duct 404 directs the cold air internally of theenclosure 401 where it is drawn into the cool air supply duct 406 formedbelow the location for the generator defined by the supporting rim 408.As previously, the cool air is drawn in to the engine-generator set forcooling and aspiration. Warmed cooling air is expelled into a warm airduct 410 below the generator where it is admixed with hot exhaust aspreviously. The mix of hot exhaust and warm air travels from the duct410 to an upright duct 412 seen in FIG. 25 and escapes through anopening 414 in a sidewall 416 of the enclosure 401.

The foregoing descriptions of at least one preferred embodiment areexemplary and not intended to limit the claimed invention. Obviousmodifications that do not depart from the spirit and scope of theinvention as claimed will be apparent to those skilled in the art. Thetoolbox containing a generator can afford portability by being movablefrom one truck to another. Also the generator is easily accessible forrepairs. In one embodiment, the toolbox is detachable from the generatorand support plenum so as to lift away from the generator and enableaccess to the generator for repairs. Further, with appropriate hinging,the toolbox lid can be opened sufficiently to permit the generator to belifted free of the box for major repairs or simply for movement to a newsite. Where the toolbox and the generator support plenum are built as asingle unit as in the exemplary embodiment of FIGS. 7 and 8, thebox-plenum combination can be sold shipped as a unit. On the other hand,where the user already has a toolbox, the separate plenum in or underthe toolbox can be provided more economically than the provision of acombined box and plenum.

1-20. (canceled)
 21. An engine-generator set installation including: (a)a plenum supporting the engine-generator set; (b) air flow means withinthe plenum including: (i) means for directing cool air from atmosphereto the engine-generator set for cooling and combustion; and (ii) meansfor directing warm cooling air away form the engine generator toatmosphere.
 22. The engine-generator set installation according to claim21, further comprising diffuser means combined with the means fordirecting warm cooling air to admit hot engine exhaust with coolerescaping cooling air.
 23. The engine-generator set installationaccording to claim 22, further including an enclosure defining alocation for the engine-generator set within, the means for directingcool air and the means for directing warm cooling air being incommunication with the location for the engine-generator set within theenclosure.
 24. The engine-generator set installation according to claim23, wherein the plenum is within the enclosure, and the means fordirecting cool air and the means for directing warm cooling aircommunicate to atmosphere through openings through the enclosure. 25.The engine-generator set installation according to claim 23, wherein theplenum is external to the enclosure, and the means for directing coolair and the means for directing warm cooling air communicate to thelocation of the engine-generator set within the enclosure throughopenings in the enclosure.
 26. The engine-generator set installationaccording to claim 25, wherein the enclosure is supported by the plenum.27. A method of cooling and aspirating an engine-generator setcomprising: (a) supporting the engine generator set on a plenum; (b)directing cooling air through the plenum to the engine-generator set tocool the engine and generator of the set and to aspirate the enginethereof; (c) directing warm cooling air through the plenum away from theengine-generator set to atmosphere; and (d) mixing hot exhaust from theengine with the warm cooling air within the plenum.